1. Field of the Invention
This invention relates to a system for removing particles from exhaust produced by engines, such as diesel engines.
2. Description of the Prior Art
Exhaust produced by diesel engines has a relatively high content of polluting particles composed of carbon, unburned fuel, and partially burned fuel. Filters disposed in engine exhaust systems are conventionally used to remove the particles from the exhaust. In this case, burners positioned in the exhaust systems upstream of the filters are often employed to burn off the particles deposited on the filters in order to unclog and rejuvenate the filters.
Japanese Patent Publication No. 59-7721 discloses such a particle removing system. This system includes a detection circuit for determining the degree of clogging of the filter. This system also includes a manual switch. Provided that the manual switch is closed, the burner is activated when the degree of clogging of the filter reaches an unacceptable level. In cases where the manual switch is open, the burner keeps deactivated even when the degree of clogging of the filter becomes unaccepable. Accordingly, there is a possibility that the filter clogs unacceptably.
Japanese Patent Publication No. 59-7720 discloses an exhaust particle removing system for an internal combustion engine. In this system, the burner is activated when the engine is stopped, provided that the filter has unacceptably clogged. As the particles deposited on the filter burn, intense heat is generated. When the engine stops, engine exhaust decreases. This exhaust decrease prevents that intense heat from diffusing smoothly and quickly. Accordingly, the filter tends to be damaged by the excessive heat.